a. Field of the Invention
The present invention relates to a method of steam-reforming of hydrocarbons, and it particularly relates to a method of manufacturing a methane-containing gas by steam-reforming of feeds of different kinds within one combined reaction system.
B. Description of the Prior Art
The method of manufacturing a methane-containing gas by steam-reforming of a mixture consisting mainly of such paraffin hydrocarbons as butane, light naphtha, etc. and steam at a temperature in the range of 400 to 500.degree.C by the use of nickel-containing catalyst has heretofore been known (cf. British Pat. No. 820,257). In the case of steam-reforming of hydrocarbons having a large mean molecular weight, however, in view of the fact that the carbonaceous material is apt to be deposited onto the nickel-containing catalyst in use for the steam-reforming, rendering it difficult to maintain the life of the catalyst for a long time and hampering smooth operation of the apparatus, it has been usual to resort to employment of an excess of steam to minimize the deterioration of the activity of the catalyst. But the employment of an excess of steam not only is uneconomical from the viewpoint of the construction cost of the apparatus as well as the thermal requirements, but also it does not always bring about an ideal composition of the resulting gas as is evident from the fact that the steam-reforming reaction of hydrocarbons may be expressed by various chemical equilibrium formulas.
As a means of overcoming such troubles, there has been proposed a method comprising the steps of introducing a mixture of hydrocarbons into the reaction zones of two or more catalyst beds distributively while introducing the whole amount of the steam into the reaction column of the first stage, thereby augmenting the ratio of the steam to the mixture of hydrocarbons within the respective reaction zones (cf. the Japanese patent publication No. 22413/1969).
British Pat. No. 1,053,855 discloses the method of introducing hydrogen into the reaction system instead of the employment of an excess of steam as a means of maintaining the life of the catalyst for a long time. And, as to the source of hydrogen for this purpose, direct application of the gas arising from a high-temperature reformer and the like have been taught therein.